It is well known that formation efficiency can be improved by increasing the adhesion between the paste and the grid. The increased adhesion between the grid and the paste provides for improved interfacial contact between the grid and the paste, thereby improving current flow between the grid and paste. Accordingly, certain efforts to improve battery formation efficiency have focused on improving the adhesion between the battery grids and the paste.
When applying battery paste to a grid, an oval-shaped wire such as that in a book mold cast grid allows the paste to flow around the wire. The rough surface and the sharp angle of the wires provide a mechanical graft and interlock of paste particles. Efforts have been made to create similar results of a book mold cast grid in a punched grid by performing a second operation to deform the cross-section of the wire after the punch operation. In this punch/deformation process, material is first punched from a strip of material to form a grid comprising a plurality of wires. The wires are then deformed such that the wire has a non-rectangular cross-section. While this punch/deformation process can help with paste adhesion, it requires additional equipment and additional unit operations compared to, for example, a punch process.
Accordingly, a need continues to exist for methods of punching and reforming openings in battery plates for lead-acid batteries with a single punch that improve paste adhesion.